Communications systems are well known and consist of many types including land mobile radio, cellular radiotelephone, satellite communications, cable television, ordinary telephone, distributed computer networks, and other communications system types. Within a communications system, transmissions are conducted between a transmitting device and a receiving device over a communication resource, commonly referred to as a communication channel.
In today's information age, there is an increasing need for high-speed data communications that provides guaranteed quality of service (QoS) to an ever-increasing number of data service users. To that end, communications networks and technologies are evolving to meet current and future demands. Specifically, networks with wider bandwidths are being deployed to handle the demand for high-speed data and communication protocols are being developed to efficiently utilize the increased bandwidth in order to reach the growing numbers of users demanding data service.
One technology known in the art that is increasingly employed to satisfy these increasing demands is broad-band communications. A broad-band communications system is one in which a single data communication channel (a shared channel) is shared by a number of end users in a coordinated manner so that data transmissions from multiple end users do not interfere with each other. In modern broad-band communications systems, the shared communication channel is typically frequency or time multiplexed over a shared physical medium. The shared physical medium may be coaxial cable, fiber-optic cable, twisted pair wires, and so on, and may also include air, atmosphere, or space for wireless and satellite communications. Since communications networks typically have a limited number of communication channels, the shared channels allow many end users to gain access to the network over a single communication channel, thereby allowing the remaining communication channels to be used for other purposes. Implementation of such a shared channel scheme is most effective when each end user only transmits data intermittently, allowing other end users to transmit during periods of silence.
Broad-band communications systems include third generation (3G) wireless cellular networks that communicate messages to and from mobile devices through a wireless cellular infrastructure. 3G is the next generation of wireless cellular technology with its primary focus on seamlessly evolving earlier wireless cellular systems to provide high-speed data services to support various data and multimedia applications, such as web page browsing. To preserve the existing wireless infrastructure, it is preferable for 3G systems to be compatible with existing voice and low-rate data capabilities of earlier systems. International mobile telecommunications in the year 2000 (IMT-2000) is the 3G specification under development by the International Telecommunications Union (ITU) that will provide standardized requirements for enhanced voice and data services over next generation wireless networks. The leading IMT-2000 proposals are based on code division multiple access (CDMA) techniques. 3G wireless cellular networks (IMT-2000 networks) include cdma2000 and wideband CDMA (WCDMA). IMT-2000 networks are often referred to as universal mobile telecommunications systems (UMTSs). However, UMTS is also frequently used when referring specifically to WCDMA.
The generalized architectural framework of a 3G wireless cellular network is based on the geographic placement of a plurality of base station transceivers, each transceiver creating a geographic coverage area known as a cell. A transceiver communicates with remote units within its cell. Such communications are maintained by the wireless cellular network as the remote units move geographically from cell to cell. In addition to multiple transceivers, the base station includes a controller, at least one control channel circuit, one or more fundamental channel circuits, one or more supplemental channel circuits, and a summer. The 3G wireless cellular network also includes at least one centralized base station controller (CBSC), at least one mobile switching center (MSC), and may include additional base stations and hardware components such as gateways and servers.
More specifically, the fundamental channels within the base station of a 3G wireless cellular network are similar to existing CDMA channels and are used primarily for voice transmissions, except spread over a wider bandwidth. In contrast, supplemental channels are utilized for communicating data transmissions to the remote unit, with the data rate of the supplemental channels being negotiated prior to transmission. Multiple data sources are time multiplexed on the supplemental channels. As such, the supplemental channels are referred to as shared channels, while fundamental channels are referred to as dedicated channels. In addition, the QoS (e.g., frame error rate (FER), bit error rate (BER), and/or transmission delay) of a supplemental channel may be set and operated independently of the fundamental channel. Both fundamental and supplemental channels are viewed as radio resources. Radio resource management, inter alia, encompasses scheduling and allocating voice and data communication signals over fundamental and supplemental channels.
Within a 3G wireless cellular network, all remote unit and base station transmissions commonly occur simultaneously within the same frequency band. This results in a received signal at a base station or remote unit that comprises a multiplicity of frequency and time-overlapping coded signals from individual remote units or base stations, respectively. Each of these coded signals is transmitted simultaneously at the same radio frequency (RF) and is distinguishable only by its specific encoding (channel). In other words, the signal received at a base station or remote unit receiver is a composite signal of each transmitted signal, and an individual signal is distinguishable only after decoding.
When a remote unit within the 3G wireless cellular network is not actively communicating to a base station, it is continuously or periodically monitoring a forward channel for notification of any pending transmission by the base station. When the base station determines that a data transmission to the remote unit needs to take place, it must determine if supplemental channel circuitry is available for handling the transmission. Shortly prior to or during supplemental channel availability, the base station notifies the remote unit of a pending data transmission via a control or fundamental channel. Control information, such as power level and other parameters necessary for communication over the supplemental channel, is forwarded to the remote unit. Finally, data transmission to the remote unit takes place utilizing the supplemental channel.
Because the number of supplemental channels available within a communications system are limited, the ability to quickly access a supplemental channel may be limited due to several remote units contending for the available supplemental channels. Under these circumstances, a supplemental channel may not be available for transmission to a given remote unit. Because of this, the remote unit will be placed in a queue until supplemental channel circuitry is available for transmission. While in the queue, the base station communicates with the remote unit on either a control channel or fundamental channel. This is dependent on the state of the remote unit. The base station will make assignments to the remote unit to minimize the transitional delay when a supplemental channel becomes available. Assignment information may include spreading codes utilized by the fundamental and supplemental channels, the data rate for the supplemental channel, and the time duration a remote unit has access to the supplemental channel. However, data transmission via the supplemental channel is prevented until a channel becomes available after an existing data transmission is either completed or dropped.
Broad-band communications systems must be able to provide an array of services to support high-speed data transmissions. One such service is a simplified method for scheduling and allocating data transmissions over communication channels for data service users in a manner that provides data service to as many users requesting service as possible, while also maintaining guaranteed QoS levels for each data transmission.
Accordingly, there is a need to improve the efficiency of broad-band communications systems when the number of users requesting data service in such a system exceeds the number of channels available for such transmissions.